A cross-sectional study of effects of industrial mercury exposure is proposed. At least 150 workers from the mercury cell chlor-alkali industry will serve as subjects. Tests will include recently developed electrophysiologic (nerve conduction) and short term memory functional measurements. Results from pilot studies of 40 workers conducted during our current longitudinal study indicate that these tests may be very sensitive in detecting the earliest subclinical effects of mercury exposure. A larger cross-sectional study is therefore necessary to evaluate the adequacy of current mercury exposure control methods. Electrophysiologic measurements will include traditional clinical measurements of nerves of upper and lower extremities in addition to new slow conduction velocity measurements. Tests of short term memory will include recently developed measurements of memory scanning rate and precision measures of memory span. All tests utilize microcomputer administration or analysis and have been developed in our current research. Correlation analysis will be used to explore possible relationships between employees' urinary mercury histories and test results. Tests similar to those mentioned above have been found to be extremely sensitive in detecting early effects of lead and carbon disulfide exposure in several large cross-sectional studies in Europe and the U.S. Our preliminary evidence strongly suggests that a similar study of mercury exposed workers must be performed to assure protection of health of these workers.